U.S. Pat. No. 5,795,551 to Powell illustrates a floating chemical dispenser for use in pools. The device exemplifies those having “mushroom” shapes, in that “a float member having a larger diameter than the floating dispenser is attached to the top end [of] the container.” See Powell, col. 4, 11. 45-47 (numerals omitted). A principal function of the larger-diameter float member is to stabilize the device. As noted in the Powell patent, “[t]he float member and the floating dispenser . . . are cooperatively defined to keep the floating dispenser erect and upright in the pool water . . . irrespective of the quantity of the contents in the container.” See id., 11. 49-54 (numerals omitted).
Another example of a floating chemical dispenser is depicted in U.S. Pat. No. 4,473,533 to Davey. Although not of mushroom shape, the dispenser of the Davey patent likewise is designed to remain stable and upright in the pool water. According to the Davey patent, “[b]y experience, the user will know [when] the container [rises] above the surface of the water to greater than a predetermined height, that the quantity of [the chemical] has been substantially depleted and must be replaced.” See Davey, col. 2, 1. 65 to col. 3, 1. 2 (numerals omitted).
U.S. Pat. No. 4,643,881 to Alexander, et al. discloses an example of a chemical dispenser which floats only when the chemical is depleted. In normal use, the dispenser rests vertically upright on a support shelf well below the water surface within the pool. As substantially all of the chemical within the dispenser dissolves, the dispenser begins to rise toward the water surface, inverting (i.e. rotating one hundred eighty degrees) as it rises. The result is that the dispenser remains in a vertical position following the inversion, albeit with its bottom floating above the water surface to alert a user that the chemical is depleted.